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Title:: Study on S₂ Foliation, Conditions of Temperature-pressure on Biotite-garnet Metacryst Minerals and the Relation of Ore-control in Jindoupo Ore Area of the Northern Hanyin, South Qinling

Author(s):: GAO Ya-ning; YANG Xing-ke ; HAN Ke; WU Xu; FAN Pei-he; 1. School of Earth Science and Resources, Chang’an University, Xi’an 710054, Shaanxi, China; 2. Key Laboratory of Western Mineral Resource and Geological Engineering of Ministry of Education, Chang’an University, Xi’an 710054, Shaanxi, China

Keywords:: S₂foliation; factor of ore-control; gold deposit; Meiziya Group; garnet-biotite geothermometer; Hanyin area; South Qinling

Abstract:: The foliation of Silurian Meiziya Group in Jindoupo ore area of the northern Hanyin, South Qinling is mostly S₂ foliation. The massive occurrence data from mapping as well as section plane based on large measuring scale indicate that the tendency of S₂foliation are 305°-355° with the dip angle of 25°-50°; the S₂ foliation, which inclines towards the north, is stable as well as placid. After comprehensive mapping and analysis, the distribution direction of S₂ foliation is mainly the same as that of gold mineralization, and has obvious constraint on mineralization. In addition, after testing the biotite-garnet paragenetic mineral assemblage from garnet-bearing biotite metacrysta sericite-schist of Meiziya Group by electron probe microanalysis, the thermal alteration temperature (590 ℃-670 ℃) was estimated by the means of Holdaway biotite-garnet geothermometer method. Comprehensive study indicates that Late Indosinian-Early Yanshanian is the metallogenic period of Au deposit, and the intense magmatic hydrothermal activities cause hydrothermal alteration and give birth to biotite metacrysta as well as garnet; the thermometamorphism accelerates the activity of Au, which has the advantage of later mineralization.